The present invention relates to content transfer technology capable of reducing the amount of usage fees to be paid for the connection bandwidth required by a first storage for connecting to a communication network by reducing the data transfer volume from the first storage to a second storage when the first storage requests the second storage to back up contents via the communication network.
In recent years, the data size of contents is increasing pursuant to the improvement in quality of video contents such as TV programs and movies being broadcast. Even households are now able to purchase and use large-capacity storages of several TB inexpensively, and record large volumes of video contents and accumulate such contents in a home storage.
Japanese Patent Laid-Open Publication No. 2005-31804 discloses a system connecting an online storage in a content storage service site that accumulates contents uploaded by users from domestic music servers, home servers, TVs and so on, and a billing and settlement service provider that offers billing and settlement service in collaboration with a download site via the Internet.
In addition, Japanese Patent Laid-Open Publication No. 2004-192602 discloses technology of automatically recovering lost data by using data that is backed up in a portal server when a home server malfunctions. This is achieved through performing data backup by periodically transferring data that is updated and accumulated in the home server, which controls and manages a home network connected to a plurality of household electrical appliances, to the portal server connected via the Internet.
Meanwhile, an online storage service is becoming popular as a new type of online service. This service is a storage capacity rental service that can be used via the Internet, and is provided for a fee or free of charge. For instance, by copying the domestic contents to an online storage, such contents can be backed up. Since the contents on the home storage side can be deleted by migrating such contents to the online storage, it is also possible to increase the unused storage capacity on the home storage side.
A domestic home storage is connected to the Internet by using a line that the user subscribed to the telecommunications carrier. The broadbandization of these lines now enables users to use a broad bandwidth of several Mbps to several ten Mbps. Nevertheless, although the data download speed of the domestic line connected to the Internet is fast, the speed of uploading data to an online server is slow. This is because the primary objective of using the Internet in homes was to download contents.
When backing up the video contents that are accumulated daily in the home storage in an online storage via the Internet, there is a problem in that the recorded data cannot be all backed up since the bandwidth of the uploading side of the line is narrow. For example, if 20 GB of video contents are once recorded and such contents are to be backed up using a line having an upload speed of 1.5 Mbps, it would take 30 hours to fully back up the foregoing video contents, and the system would fail since the backup cannot be completed in a single day.
Conventionally, technology for overcoming this problem depended on compressing the transmitted data or sending only critical data.